U.S. patent number 3,971,753 [Application Number 05/424,281] was granted by the patent office on 1976-07-27 for polymer composites and preparation thereof.
This patent grant is currently assigned to Union Carbide Corporation. Invention is credited to Arthur C. Frechtling, Norman W. Johnston, Richard G. Shaw.
United States Patent |
3,971,753 |
Frechtling , et al. |
July 27, 1976 |
Polymer composites and preparation thereof
Abstract
Polymer composites having enhanced mechanical or chemical
properties have been prepared by first coating the filler component
of the composite with a free-radical polymerization initiator which
adheres to the surface of the filler and then polymerizing an
ethylenically unsaturated monomer onto the filler.
Inventors: |
Frechtling; Arthur C.
(Watchung, NJ), Johnston; Norman W. (East Windsor, NJ),
Shaw; Richard G. (Asbury, NJ) |
Assignee: |
Union Carbide Corporation (New
York, NY)
|
Family
ID: |
23682105 |
Appl.
No.: |
05/424,281 |
Filed: |
December 13, 1973 |
Current U.S.
Class: |
524/789; 428/404;
428/406; 523/218; 525/227; 525/232; 525/239; 525/241; 428/407;
524/790; 525/228; 525/238; 525/240 |
Current CPC
Class: |
C08F
292/00 (20130101); C08K 9/04 (20130101); Y10T
428/2998 (20150115); Y10T 428/2993 (20150115); Y10T
428/2996 (20150115) |
Current International
Class: |
C08F
292/00 (20060101); C08K 9/00 (20060101); C08K
9/04 (20060101); C08K 009/04 (); C08K 009/10 () |
Field of
Search: |
;260/42.14,42.53,42.16,17.4R,17.4GC,17.4CL,17.5,857G,873,878R,879,881,884 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Derrington; James H.
Attorney, Agent or Firm: Crowe; Bernard Francis
Claims
What is claimed is:
1. A composite comprising a filler substrate, an organic free
radical polymerization initiator, which has been decomposed into
free radicals, containing carboxyl or carboxamide groups, said
initiator bonded through said groups to said substrate and
ethylenically unsaturated monomer which has been polymerized to a
resin matrix by said initiator free radicals.
2. Composite claimed in claim 1 wherein the resin matrix is
polyacrylonitrile.
3. Composite claimed in claim 1 wherein the resin matrix is
polystyrene.
4. Composite claimed in claim 1 wherein the resin matrix is
polymethyl methacrylate.
5. Composite claimed in claim 1 wherein the resin matrix is
polyethyl acrylate.
6. Composite claimed in claim 1 wherein the resin matrix is
polyvinyl chloride.
7. Composite claimed in claim 1 wherein the resin matrix is a
styrene-acrylonitrile copolymer.
8. Composite claimed in claim 1 wherein the filler substrate is in
fiber form.
9. Composite claimed in claim 1 wherein the filler substrate is in
sheet form.
10. Composite claimed in claim 1 wherein the filler substrate is in
particulate form.
11. Composite claimed in claim 1 wherein the filler substrate is
glass.
12. Composite claimed in claim 1 wherein the filler substrate is
asbestos.
13. Method of fabricating a composite which comprises the steps
of:
a. coating the surface of a filler substrate with a free radical
organic polymerization initiator containing carboxyl or caboxamide
groups having an affinity for and which adhere to the surface of
said substrate;
b. contacting the initiator coated substrate with an amount of an
ethylenically unsaturated monomer sufficient to at least cover the
total surface area of said initiator coated substrate; and
c. maintaining the temperature of the initiator coated substrate
ethylenically unsaturated monomer combination at a point where the
initiator decomposes to form free radicals until a layer of the
ethylenically unsaturated monomer polymerizes on the substrate.
14. Method claimed in claim 13 wherein the substrate is glass.
15. Method claimed in claim 13 wherein the substrate is
asbestos.
16. Method claimed in claim 13 wherein the ethylenically
unsaturated monomer polymerized on the substrate at a temperature
of about 10.degree. to about 140.degree.C.
17. Method claimed in claim 13 wherein the ethylenically
unsaturated monomer is acrylonitrile.
18. Method claimed in claim 13 wherein the ethylenically
unsaturated monomer is polymerized in bulk.
19. Method claimed in claim 13 wherein the ethylenically
unsaturated monomer is polymerized in a non-aqueous diluent.
20. Method claimed in claim 13 wherein the polymerization initiator
is t-butyl peroxy maleic acid.
21. Method claimed in claim 13 wherein the polymerization initiator
is t-butyl azoformamide.
22. Method claimed in claim 13 wherein the polymerization initiator
is 4-t-butylazo-4-cyanovaleric acid.
23. Method claimed in claim 13 wherein the polymerization initiator
is succinic acid peroxide.
Description
BACKGROUND OF THE INVENTION
This invention pertains to polymer composites and more particularly
to those containing a filler polymerization initiator complex onto
which an ethylenically unsaturated monomer has been
polymerized.
Composite material systems consisting of a thermoplastic resin
matrix reinforced with a filler have found wide use as structural
materials. The effectiveness of the fillers as reinforcing agents
is directly related to the adhesion between the filler and the
matrix resin. If the adhesion between the matrix resin and the
filler is poor as in the case of poor wettability of the filler by
the matrix resin, the reinforcing effect of the filler is limited
and may actually be deleterious in the extreme case of very poor
adhesion.
SUMMARY OF THE INVENTION
A composite having enhanced mechanical and physical properties is
provided by:
A. coating the surface of a filler substrate with a free radical
polymerization initiator containing polar functional groups having
an affinity for and which adhere to the surface of said
substrate;
B. contacting the initiator-coated substrate with an amount of an
ethylenically unsaturated monomer sufficient to at least cover the
total surface area of said substrate; and
C. adjusting the temperature of the initiator coated
substrate-vinyl monomer combination to a point where the initiator
decomposes to form free radicals until a layer of the ethylenically
unsaturated monomer polymerizes on the substrate.
DESCRIPTION OF THE INVENTION
The resins which can be used as the matrix in the composites of
this invention are myriad. For example, they can include polyalkyl
acrylates, polyalkyl methacrylates, wherein each have 1 to about 18
carbon atoms in the alkyl group, polyacrylonitrile, polystyrene,
polyvinyl chloride, vinyl chloridevinyl acetate copolymers,
polybutadiene, polyisoprene, polyethylene, polypropylene,
acrylonitrile-butadiene-styrene copolymers and like vinyl or
addition thermoplastic polymers.
Fillers which can be used as the substrate of this invention are
legion and include both organic as well as inorganic materials.
Exemplary of the organic materials which can be used are cellulosic
products including wood products in form of kraft paper, chips,
coarse flour, gram flour, and the like, comminuted cellulose
products, including chopped paper, diced resin board, pulp
preforms, and the like; fibers including alpha cellulose, cotton
flock, jute sisal, rayon and the like; lignin products including
ground bark and processed lignin; synthetic fibers including
polyamides such as nylon, polyesters, such as polyethylene
terephthalate, polyacrylonitrile and the like; carbon in the form
of carbon black including either channel black or furnace black,
ground petroleum coke, graphite filaments, graphite whiskers, and
the like. Among the inorganic fillers which can be used are silica
products including minerals such as sand, quartz, tripoli,
diatomaceous earth, and the like and synthetic materials including
wet process silica, pyrogenic silica, silica aerogel, and the like;
silicates including minerals such as asbestos in the form of
chrysotile, amosite, anthophyllite, crocidolite, tremolite, or
actinolite, kaolinite, mica, nepheline, syenite, talc, or
wollastonite as well as synthetic silicates including calcium
silicate and aluminum silicate; glass in the form of glass flakes,
hollow glass spheres, solid glass spheres, milled fibers, fibrous
glass in the form of filament, rovings, woven roving, yarn, mat, or
fabric; metals such as steel, tungsten, titanium, beryllium
filaments, molybdenum filaments; boron filaments; metallic oxide
including zinc oxide, aluminum oxide, magnesium oxide, titanium
oxide, thorium oxide, zirconium oxide, and the like; calcium
carbonate in the form of chalk, limestone, or precipitated calcium
carbonate; polyfluorocarbons and the like.
A further ramification of this invention is its extension to the
use of fillers in composites having as its primary purpose one
other than solely as a reinforcement for improving mechanical or
physical properties of a matrix resin. For example, discrete
particles of diammonium phosphate, ammonium sulphamate,
hexabromobenzene or other known fire retardants can have
polymerized onto them a continuous covering of an organic polymer
and then blended in or dispersed through a matrix resin to afford a
flame retarded composite. This procedure provides a continuous
interfacial boundary around the fire retardant particles and
prevents their migration into or out of the resin matrix providing
a composite which does not change upon storage or aging. In such a
system the flame retardant is suitably dispersed and is available
to perform its function, should the need arise, upon exposure to
incindiary temperatures. This technique is particularly applicable
to water soluble fire retardants which can be leached out of
articles in which they have been deposited. Thus, e.g., less than
1% of methyl methacrylate polymerized onto diammonium phosphate
previously treated with succinic acid peroxide lowers the
solubility considerably. The use of a crosslinking monomer, such
as, divinyl benzene lowers the solubility even more.
The instant invention can also be practised in conjunction with
conventional polymerization techniques. Thus, for example, polymer
coated filler substrate particles can first be prepared and these
can then be introduced into a polymerization system where
conventional polymerization initiation is used. The polymer formed
in the latter step collapses around the polymer coated substrate
particles.
The term "composite" as used in this invention is intended to
encompass products obtained by combining a resin matrix with a
filler in a general sense as well as systems in which the filler
functions as a reinforcement for the resin matrix in a synergistic
relationship, i.e., the physical and mechanical properties of these
products are superior to those of both the resin matrix and the
reinforcing filler alone. This concept also includes such terms as
laminates and reinforced plastics since there is no rigid
definition universally accepted in this art.
The bonding of organic polymer to the surface of the reinforcing
filler substrate is effected by coating the surface of the
reinforcing filler substrate with a free radical polymerization
initiator containing one or more polar functional groups having an
affinity for and which adhere to the surface of said substrate
followed by contacting the initiator coated substrate with an
amount of an ethylenically unsaturated monomer sufficient to at
least cover the total surface area of said substrate and then
raising the temperature of the initiator coated substrate --
ethylenically unsaturated vinyl monomer combination to a point
where the initiator decomposes to form free radicals attached to
the substrate and maintaining this temperature until a layer of the
ethylenically unsaturated monomer polymerizes on the substrate.
The selection of ethylenically unsaturated monomers for the
preparation of suitable organic polymers is not narrowly critical
but preferred monomers include acrylonitrile, alkyl acrylates or
methacrylates having 1 to about 18 carbon atoms in the alkyl group,
i.e., methyl through octadecyl acrylates or methacrylates, vinyl
chloride, styrene, divinyl benzene, and the like.
The above listed monomers can be used alone or in combination to
form homopolymers or copolymers. The monomer feed may also be
varied qualitatively to afford graded layers of different polymer
species.
It will be understood by those skilled in the art that the
composites available may consist simply of filler and a single
extensive continuous polymer phase or filler particles or segments
may be first coated with a layer of polymer and in a second step
the polymer coated filler blended with a quantity of the same
polymer or another polymer or combination of polymers. The latter
procedure affords a means of improving compatibility between filler
and polymer where it is desired to prepare a filler reinforced
composite in which the uncoated filler and the continuous polymer
phase are not compatible.
If the non-aqueous suspension polymerization technique is to be
used, the procedure described in U.S. Pat. No. 3,519,701 for the
preparation of polyvinyl esters and derivatives therefrom can be
used and this reference is incorporated herein.
The choice of free radical polymerization initiators is not
narrowly critical but as will be recognized by those skilled in art
it will depend in part upon the ethylenically unsaturated monomer
being polymerized. Therefore it is preferred to use an initiator
having a half life which provides a reasonable polymerization rate
at the optimum polymerization temperature of the particular
ethylenically unsaturated monomer used. The other requirement for
the choice of polymerization free radical initiator is that its
molecule contains the polar group which will anchor or adhere the
free radical polymerization initiator to the surface of the filler
substrate and which will remain intact after the decomposition of
the initiator into free radical form. Preferred polar functional
groups are carboxyl groups, carboxamide groups, hydrocarbyl amines,
hydrocarbyl hydroxyls, and the like.
A preferred free radical polymerization initiator meeting the above
criteria is succinic acid peroxide. Other free radical initiators
meeting these criteria include t-butyl peroxy maleic acid,
t-butylazoformamide and 4-t-butylazo-4-cyanovaleric acid.
The invention is further described in the Examples which follow.
All parts and percentages are by weight unless otherwise
specified.
EXAMPLE 1
A four neck, 250 ml. glass resin kettle equipped with a Teflon
anchor type stirrer, reflux condenser, thermometer and nitrogen gas
inlet tube was charged with 200 grams of glass spheres (size 3000
obtained from Potter Brothers Inc. having an average diameter of 30
microns) which had previously been soaked in a solution of succinic
acid peroxide in methanol and then dried to afford a total weight
of 1.2 grams of succinic acid peroxide on the 200 grams of glass
beads. Then 20 grams of acrylonitrile and 60 grams of normal
heptane were added to the kettle. This mixture was heated for two
hours at a temperature of about 73.degree. to 75.degree.C. with
stirring under an atmosphere of nitrogen. The beads were removed
and dried and found to contain a total coating weight of 1.2 to
about 1.4 weight per cent of polyacrylonitrile. These coated beads
were then extracted for five hours in hot gamma-butyrolactone,
removed and dried again. By weighing it was ascertained that about
0.5% by wt. of polyacrylonitrile was retained on the surface of the
glass beads. A composite was prepared by blending 30% by wt. of the
above treated glass beads into an acrylonitrile-styrene copolymer
(having 72% by wt. of styrene copolymerized therein and an inherent
viscosity of about 0.8 when measured at a concentration of about
0.2 grams in 100 ml. of methyl ethyl ketone at 30.degree.C.).
Various mechanical and physical properties of sheets of the above
prepared composite were determined and recorded in Table I. These
values were compared with control A, a composite which employed the
same acrylonitrile-styrene copolymer with 30% by wt. of untreated
glass beads. The data obtained from this composite are also
presented for comparison in Table I.
TABLE I ______________________________________ Mechanical and
Physical Example 1 Properties of Styrene- Control A (Glass Beads
Acrylonitrile Copolymer/ (Untreated Coated with Glass Bead
Composite Glass Beads) Polyacrylo- nitrile)
______________________________________ Flexural Strength, 10.sup.3
psi (ASTM D790-59T) 9.4 13.4 Flexural Modulus 10.sup.5 psi (ASTM D
790-59T) 5.8 8.3 Tensile Strength 10.sup.3 psi (ASTM D 638-60) 6.4
6.5 Tensile Modulus 10.sup.5 psi (ASTM D 638-60) 4.5 5.3
Elongation, % (ASTM D 638-60) 2.5 2.2
______________________________________
EXAMPLE 2
When Example 1 is repeated with the exception that styrene is
substituted for the acrylonitrile, the polystyrene coated glass
beads also improve the mechanical properties of composites into
which they are blended.
EXAMPLE 3
Using the polymerization procedure described in Example 1, 100
grams of methyl methacrylate were subjected to polymerization with
glass beads coated with succinic acid peroxide. The glass beads
isolated contained a coating of polymethyl methacrylate. When these
are used in composites with a polymethyl methacrylate matrix
enhanced mechanical properties are observed.
EXAMPLE 4
Using the polymerization technique described in Example 1 with 100
grams of ethyl acrylate and glass beads coated with succinic acid
peroxide the resultant beads were coated with polyethyl acrylate.
These coated beads serve to enhance the mechanical properties of
polyethyl acrylate matrix resins.
EXAMPLE 5
Using the polymerization procedure described in Example 1 with 100
grams of vinyl chloride as the monomer, glass beads were isolated
containing a coating of polyvinyl chloride. These coated beads
enhanced the mechanical properties of polyvinyl chloride
matrices.
EXAMPLE 6
Using the procedure described in Example 1, 100 grams of dodecyl
methacrylate was polymerized with succinic acid peroxide coated
glass beads. The glass beads isolated contained a coating of
polydodecyl methacrylate. These coated beads enhanced the
mechanical properties of polyethylene matrices.
EXAMPLE 7
Using the procedure described in Example 1 with the exception that
100 grams of dodecyl methacrylate was used as the monomer and rayon
fibers soaked in succinic acid peroxide were used in place of the
glass beads. These were obtained rayon fibers coated with
polydodecyl methacrylate. These coated fibers can be used to
enhance the mechanical properties of rayon matrices.
EXAMPLE 8
The procedure used in Example 1 was employed with 100 grams of
t-butyl peroxy 10-undecenoate and glass beads coated with succinic
acid peroxide. The beads which were isolated contained a coating of
poly-t-butyl peroxy 10-undecenoate. These coated glass beads can be
used to enhance the mechanical properties of polyethylene.
EXAMPLE 9
Using the procedure described in Example 1, 100 grams of butadiene
was polymerized onto clay which had been coated with succinic acid
peroxide. The clay was isolated with a coating of polybutadiene
which when blended into polystyrene acted as an impact modifier and
the resultant composite was found to be 30% more improved in impact
properties than the same composite made with polybutadiene
alone.
EXAMPLE 10
Using the polymerization technique described in Example 1, 100
grams of diammonium phosphate particles having an average particle
size of about 5-10 microns was first coated with succinic acid
peroxide and then used to polymerize 30 grams of methyl
methacrylate onto the surface of these particles. The coated
diammonium phosphate particles when blended into a resin matrix of
polymethyl methacrylate imparts fire retardant properties to the
polymethyl methacrylate matrix.
The time required for 5 g. of uncoated diammonium phosphate
particles to dissolve in cold water was 45 seconds. After coating
with polymethyl methacrylate as described above 20 to 25% of the
particles were still insoluble after twenty washings with water at
80.degree.-90.degree.C. with the duration of each washing being
fifteen minutes.
When divinyl benzene was used as the monomer in this experiment in
place of the methyl methacrylate, 83% of the coated particles were
insoluble after twenty washings.
EXAMPLE 11
Using the procedure delineated in Example 1 methyl methacrylate was
polymerized onto glass beads which has been previously soaked in a
methanolic solution of t-butyl peroxy maleic acid (TBPMA). The
beads were dried, extracted in hot gamma-butyrolactone, and dried
again and weighed. The polymer coating was then burnt off and by
the difference in weight was found to amount to 0.6% by weight.
In Contrast Control B, which consisted of glass beads which were
unreacted with initiator or monomer, taken through the steps of
Example 11 showed a weight loss of only 0.1%.
Similarly Control C, which consisted of repeating Example 11 but
with the exception that the non-polar initiator t-butyl peroxy
privalate was used in place of the TBPMA, showed a weight loss of
treated glass beads of only 0.1%.
EXAMPLE 12
Example 11 was repeated substituting t-butyl azoformamide (TBAF)
for the TBPMA. The polymethyl methacrylate burnt off the glass
beads amounted to 0.3% by weight.
EXAMPLE 13
Example 11 was repeated substituting t-t-butyl peroxy maleic acid
for the TBPMA. The polymethyl methacrylate burnt off the glass
beads amounted to 0.5% by weight.
Although the invention has been described in its preferred forms
with a certain degree of particularity, it is understood that the
present disclosure of the preferred forms has been made only by way
of Example and that numerous changes may be resorted to without
departing from the spirit and scope of the invention.
* * * * *